Best time to Dyno

The optimal dyno day is 55~65 degrees and low humidity.
MOST shops service department/dyno areas are not temperature controlled so do not bank on that.

Having an experienced dyno operator is key.

Most dealership operators are used to installing a map or changing the main jet, you need a carburetor or EFI tuner that knows how to equate throttle position to the carb/efi and make the proper adjustments.

Get before and after powercurves so that you can note what the operator did to achieve the results, this way you know what set up you had and where you are now at, this way if ambient conditions change vastly you can make an educated change to the set up.

We can talk all day about dynos, the room they are run in, correction factors etc, the big key is that the air is recirculated in the room so that the runs are not corrupt from "bad air".

You cannot ride a dyno, runs are typically made at WOT, an Eddy current dyno is a better choice for tuning properly.

Hope that helps.

ohiomotoxer

Thanks for the information. I figured a warmer day would be somewhere in the middle of the road for tuning so that's what I'll try to shoot for when I setup my appointment.

I also put the SuperTrapp 2:1 on the bike. I started out with 16 discs and it was to loud for my taste. I went down to 12 discs as you suggested and it's quieter. As for torque it's hard to tell due to the fact that it's still breaking in. My next move is to try the open cap with 12 discs as you suggested also.

When tightening the end cap how tight is to tight? Do I tighten in a criss cross patten until I see the discs stop compressing, then just snug the screws gently? Even then the screws seem to be very loose?

The bike really pulls great from 2000 to 4000 rpms( Dealer says not to exceed 4000 rpms until 500 mi. breakin). I couldn't be happier with the stage 2 build, SERT and SuperTrapp so far. I can't imagine it's going to be better after the dyno tunning.

Thanks for the advice on both the dyno and SuperTrapp.

Steve

Here's a collage of dyno info I've put together from various internet sources to help me understand what influences dyno tuning.

Dyno comparison should be used for fun to see what various performance builds have the potential to produce. Dyno testing in general can be misleading and should only be used to show changes in power delivery on the same bike, on the same dyno, on the same day. Dynoing the same bike on different days will net different results. Variables such as dyno operator, dyno calibrations, humidity, air temperature, engine temperature, weight of the tester, tire inflation, tire temperature, tire diameter, Gear ratios, correction factors, engine and oil temperatures, type and weight of oil, vehicle mounting procedures, clutch slippage, and the amount of engine break-in or wear can all affect the test.

The dyno is nothing more than another shop tool and is only as effective as the operator, just like any other tool. When used properly it will aid dramatically in performance improvement. If you want to compare your bike to your friend's bike, you will need to go to the dyno together. Dyno charts that are made on different days are not always comparable. This is especially true if there were very different temperature or humidity conditions. Always use the same dyno, under conditions as close as possible to the original run. This means returning when the weather conditions are the same, running your bike at the same engine temperature every time and changing only those parameters you want to test, one at a time.

A well set up, professional dyno shop will usually have a dyno “cell.” The cell is nothing more than a purpose built room with sound deadening and airflow and climate control systems that help control many of the environmental variables that affect power measurements. With a cell, dyno runs can be conducted all day long and good comparisons can be made.

The mere reading of horsepower and torques is almost meaningless (aside from occasional “bragging” rights) in and of itself. But when you want to diagnose a little misfire, see if the engine is running lean in the mid-range, or verify that a cam change actually helped the power-band, you can’t beat a dyno.

The dyno will correct (hence “corrected” horsepower) for atmospheric conditions, within limits but a run on the hottest day of the year and a run during a blizzard aren’t likely to be comparable.

How's it calculated? One common use of the dyno correction factor is to standardize the horsepower and torque readings, so that the effects of the ambient temperature and pressure are removed from the readings. By using the dyno correction factor, power and torque readings can be directly compared to the readings taken on some other day, or even taken at some other altitude.

The Society of Automotive Engineers (SAE) has created a standard method for correcting horsepower and torque readings so that they will seem as if the readings had all been taken at the same "standard" test cell where the air pressure, humidity, and air temperature are held constant.

A key element to producing comparable dyno charts on a global basis is the Correction Factor, SAE Standard J1349, which applies the following weather station data--atmospheric pressure 29.23, air temperature 77 degrees Fahrenheit and humidity 0 percent--to all tests. These exact figures allow apples-to-apples comparison of runs from different cars, different facilities, etc. So graphs with SAE-corrected power were made to this standard. The dyno in question must have a weather station and the proper software in order to generate SAE-corrected data.

SAE -- The SAE standard applied is a modified version of the SAE J1349 standard of June 1990. Power is corrected to reference conditions of 29.23 InHg (99 kPa) of dry air and 77 F (25°C). This SAE standard requires a correction for friction torque. Friction torque can be determined by measurements on special motoring dynamometers (which is only practical in research environments) or can be estimated. When estimates must be used, the SAE standard uses a default Mechanical Efficiency (ME) value of 85%. This is approximately correct at peak torque but not at other engine operating speeds. Some dynamometer systems use the SAE correction factor for atmospheric conditions but do not take mechanical efficiency into consideration at all (i.e. they assume a ME of 100%). SuperFlow uses a more sophisticated algorithm for calculating friction torque, based on a summary of thousands of friction power tests performed by the automotive industry. This proprietary algorithm estimates friction torque as a function of piston speed and engine displacement.

STD -- The STD (also called STP) standard is another power correction standard determined by the SAE. This standard has been stable for a long time and is widely used in the performance industry. Power is corrected to reference conditions of 29.92 InHg (103.3 kPa) of dry air and 60 F (15.5°C). Because the reference conditions include higher pressure and cooler air than the SAE standard, these corrected power numbers will always be about 4 % higher than the SAE power numbers. Friction torque is handled in the same way as in the SAE standard. Once again, this means the STP corrected power displayed by your SuperFlow test system will be more accurate than power numbers obtained using a default Mechanical Efficiency of 100% or 85%.

ECE -- The ECE standard is based on the European Directives. Power is corrected to reference conditions of 99 kPa (29.23 InHg) of dry air and 25°C (77 F). Friction torque is not taken into consideration at all.

In 1995, a new Directive (95/1/EEC) regarding test methods for motorcycles was published. The CycleDyn uses some of the information provided in this standard as reference for driveline loss calculations.

DIN -- The DIN standard is determined by the German automotive industry. Power is corrected to reference conditions of 101.3 kPa (29.33 InHg) of dry air and 20°C (68 F). With the advent of European legislation and standards, national standards such as the DIN (formerly widely used) are now less significant.

4th Gear vs. 5th Gear: In high gear, the input and output shafts are simply locked together, giving a 1:1 ratio and minimal power loss. The input shaft also meshes with a gear on a countershaft mounted beside or below it. This countershaft is often referred to as the cluster gear or shaft because it also has a gear for each of the transmission’s lower gears. To complete power transmission in the lower gears, the output shaft has mates for the gears on the cluster. The ratio of each lower gear is a combination of the reduction ratios of the input-to-cluster and cluster-to-output gears. So in each of the lower gears power goes through two gear meshes, producing — you guessed it — double the power loss.

5th gear is the direct drive gear. So you will not have the mechanical power robbing disadvantage of sending power through the other shafts in the gearbox. Subsequently you are going to see higher numbers in fifth than in fourth because of that advantage.

The deal with "what gear to run" was started in 4th gear when the EVOs were around and stock, they couldn't pull 5th (1:1) gear, and the bikes (touring rigs) would go faster in 4th than 5th.

When the TC came out with more torque it could pull 5th so naturally 5th (1:1) was correct, until the 6 speed direct drive (1:1) transmissions surfaced. Now, if the engine has enough torque to pull the overall higher ratio BUT STILL 1:1, that becomes the proper gear. But, if the engine is bone stock 6th is too tall for the same reason the EVO 5th was too tall.

All we are doing here is trying to dyno tune using the gear with the least loss through the tranny, whether it be 5th or 6th, whatever is direct drive (1:1).

Power readings recorded in fifth gear are generally higher than those performed in fourth gear.

Also, a final drive ratio of 3.15:1 will often show a higher power reading than a 3.37:1 ratio. With a 3.15:1 final drive ratio, the greater the engine loading and higher the power reading will be. Since the 3.15:1 gear ratio slows the engine’s acceleration rate, less power is required to accelerate the rotating and reciprocating parts.


Hot Run vs. Cool Run The first dyno run when the engine is cool usually produces the biggest power. As heat builds in the engine, the peak power number usually settles at a lower level. Oil temperature has a significant effect on engine power.

Most bikes make more power on their first Dyno pull while everything is still nice and cool. If you allow a reasonable cooldown period between runs (only a minute or two is needed on most bikes) all the subsequent runs should be consistent with each other. The natural inclination of anybody trying to show a power gain, though, is to use a lower, hot run as the baseline, and a nice, strong cold run to showcase their part .

Every Dynojet has a small weather station built in to feed the appropriate temperature and barometric pressure readings to the computer so it can calculate this factor. The difference between 0 percent and 100 percent humidity is about a seven percent correction. A temperature change from 60 to 90 degrees, on the other hand, will have an effect of about a 2.8 percent. A difference in elevation from sea level to 5000 feet is worth a whopping 20 percent!

Daisy Chain/Rapid-Fire Runs Performing back-to-back-to-back pulls without ample cooling time between runs can cause an unnatural buildup of heat. This will adversely affect the before-and-after testing of components. The goal is to conduct testing at consistent, normal engine operating temperatures.

The Density Intensity Game Another way of cheating is to play the density intensity game - conducting baseline runs in the heat of the afternoon and run the after-tests in the cool evening air. While some dynos can adjust for atmospheric conditions, the bottom line is denser air makes more power.

Beat the Drum The crooked dyno operator can reprogram the weight of the drum, which will allow the dyno to create anomalous power numbers.

Change Load Changing the load by tightening or loosening the tie-down between runs can compromise any comparisons made with the dyno testing.

Messing With the Weather This is where the dyno operator has to be extremely devious. If you mess with the readings that the computer uses to calculate the correction factor, you can alter the corrected output significantly. The one reading that the built-in sensors do not take automatically is humidity. The dyno operator has to enter the humidity correction themselves. Since the humidity is manually entered into the computer it is the easiest to alter. While humidity numbers are obviously suspect, the temperature can be faked pretty easily as well. Another good way of bumping up the power figures is by "playing about" with the air temperature and pressure corrections. If you dial in your own "standard" conditions as being freezing cold with the barometer going off the scale, or you put the temperature probe near the engine, you can get the system to add huge amounts of power to what was actually measured. So make sure you know if such corrections were made or not and to what standards they were made if any. We actually decided to try this one, just to see how easily it could be done.

Jackson Racing's Dynojet is set up with the weather data box mounted on a perpetually-shady portion of the dyno room wall. The temperature probe hangs under the box in the open air about two feet off the ground--right where most air intakes pull their air supply. Oscar Jackson pointed out that he has seen these boxes mounted where they were more easily accessed, and has even seen the temperature sensor hanging on a divider wall next to the computer, or in a drawer on the dyno bench. In the drawer, an unscrupulous dyno operator could put his or her hand around the sensor before doing a run, bumping the ambient temperature reading up into the 90-degree range. With it hanging on a well-placed wall, the sensor could be flipped from the shade into direct sunlight, where it could slowly bake up to a nice, warm temperature.

The wire on Jackson's sensor was only about two feet long, so we couldn't get it into the sun, and a shield prevented holding the sensor in a warm hand from having much effect. Instead, I cupped my hands around the sensor and blew on it. Within 30 seconds the dyno was reading 95 degree ambient temperatures even though our baseline run made a few minutes earlier had been in 66-degree air. We made another run with the engine breathing 66-degree air, but the dyno correcting for 95-degree air. Our corrected power jumped from 136 hp to 143 hp.

Correction factors between 0.97 and 1.03 are pretty normal. Outside that range, you should be on the lookout for large differences between the runs you are comparing.

In order for dyno results to be comparable and universally understood there are a number of things that need to be closely controlled during the measurement process: Operating Conditions - air temperature, pressure and humidity affect the amount of power an engine produces. Cold dense air means a greater mass of oxygen per power cycle and thus more power is generated (provided of course that air/fuel mixture is properly calibrated for the conditions prevailing). There are formula that can be used to calculate how much the measured power would change if the test conditions were different. This enables dyno results to be "corrected" back to standard conditions to enable comparison with anyone else's test results. Sadly however there is no one universally accepted set of "standard" conditions because different automotive bodies in different countries use different standards to calibrate to. "SAE" power standards are used in the USA and sometimes in England. "DIN" standards are used in Europe and there are a few other oddball systems just to confuse the issue. So just because your car is rated at 100 bhp and a friends at 110 bhp doesn't necessarily mean that his engine is more powerful - it depends whether both measurements were corrected to the same standard conditions.

From Short Block Charlie 7/24/04 One of the big problems I see with dyno charts is the following. Was the dyno test performed in a dyno cell? A dyno cell is designed to input air and remove exhaust for proper tests. If not, you will see false readings. Very few dyno facilities have this, such as the traveling dyno tuners. The dyno has the capableness to compensate for humidity and elevation to record corrected information. The other problem I have with my own customers is they will get a dyno sheet that is not impressive, but bike runs like rocket ship. There is a lot of magic out there to fool the consumer.

An engine's output depends on the quality of air it breathes, and it is therefore essential to take into account variances in air pressure, temperature and humidity when measuring horsepower. Raw numbers are generally normalized to sea level conditions within a dynamometer's software using a standard correction factor. However, this does not mean you will get identical readings from two different dynos, or for that matter, the same dyno on two different days. While the dynamometer corrects the horsepower it reads to standard atmospheric conditions, it cannot account for jetting changes you should have made to account for the weather. For example, you could run your bike at the local dyno and see 100 corrected horsepower on a cold day and return--without changes--on a hot day for another run and get 98 corrected horsepower. Where's the two horsepower? To get back to 100 horsepower, you'd have to lean your bike out for the hotter weather. Because different weather conditions can result in different air densities and different oxygen concentrations, the weather can have a significant effect on power output. The SAE has a standard set of correction factors that can be used to normalize all power outputs to what they would be at sea level, on a 60 degree day, with 0 percent humidity. Every Dynojet has a small weather station built in to feed the appropriate temperature and barometric pressure readings to the computer so it can calculate this factor. The difference between 0 percent and 100 percent humidity is about a seven percent correction. A temperature change from 60 to 90 degrees, on the other hand, will have an effect of about a 2.8 percent. A difference in elevation from sea level to 5000 feet is worth a whopping 20 percent!

Operating Conditions Altitude, air temperature, pressure and humidity affect the amount of power an engine produces. The only thing to really worry about is the A to B changes on the same bike, same dyno, same day.
Sometimes you may want to know how much power you are really making on that specific day due to the temperature, humidity and pressure on that day; in that case, you should look at the uncorrected power readings.
When you want to see how much more power you have solely due to the new exhaust or the new cam, then you will find that the corrected power is more useful. It removes the effects of the temperature, humidity and atmospheric pressure and just shows you how much more (or less) power you have than in your previous tests.

Altitude As you increase your altitude the octane requirement decreases 1-2 octane per 3000 feet elevation. This is because the density of the air is reduced or there is less air available for your motor to burn. The higher the altitude, the richer your motor will run, making it necessary to re-jet the motor in order to lean it out. The fuel volume remains the same and the air volume goes down. If you have a vacuum advance, as the altitude increases, the motor makes less vacuum and the air fuel ratio becomes richer due to the decreasing air to fuel volume. Altitude and weather systems change the air's pressure. As you go higher, the air pressure decreases from around 1,000 millibars at sea level to 500 millibars at around 18,000 feet. Most of us race at less than 1000 feet of elevation. Weather systems that bring higher or lower air pressure also affect the air's density, but not nearly as much as altitude. Air density is lowest at a high elevation on a hot day when the atmospheric pressure is low, say in Denver when a storm is moving in on a hot day. The air's density is highest at low elevations when the pressure is high and the temperature is low, such as on a sunny but extremely cold, winter's day in New Hampshire. Humidity and air density Most people who haven't studied physics or chemistry find it hard to believe that humid air is lighter, or less dense, than dry air. How many times have you heard someone tell you to add more gear on a hot humid day because it is harder to push the kart through the hot humid air. The inverse is really true, the kart flows easier through the air but the pressure needed to fill the cylinder with the proper air fuel mixture is lessened by lowered air density.

Temperature When the temperature goes up, the air density decreases, thus you have less air available for combustion and your air fuel ratio becomes richer. The same works in reverse. As the temperature goes down, you end up with more air per cubic foot, and without re-jetting your carburetor, the engine will run leaner.

Air Density As the air density increases, your engine will lean out. As the air density goes down, the engine runs richer. Like driving up a mountain, at the top, the motor has less power because you have less air to burn. Cold dense air means a greater mass of oxygen per power cycle and thus more power is generated (provided of course that air/fuel mixture is properly calibrated for the conditions prevailing). Air density is a combination of two factors: barometric pressure and temperature. At 85 degrees Farenheight and at 29.92 inches of mercury for barometric pressure (at normal sea level) air density is considered to be at 100%. The horsepower and torque available from a normally aspirated internal combustion engine are dependent upon the density of the air... higher density means more oxygen molecules and more power... lower density means less oxygen and less power.

The relative horsepower, and the dyno correction factor, allow mathematical calculation of the affects of air density on the wide-open-throttle horsepower and torque. The dyno correction factor is simply the mathematical reciprocal of the relative horsepower value.

Air density is affected by the temperature, pressure and humidity of the air. On a hot day, or at high altitude, or on a moist day the air is less dense which means that there is less oxygen available for combustion which, in turn, means that there is also less engine horsepower and torque.

Vapor Pressure Humidity or vapor pressure is an important factor in calculating the corrected horsepower and torque values. An abnormally high vapor-pressure figure will inflate the torque and power numbers. Cool days typically produce 0.3-0.4 vapor-pressure readings. You'll likely see 0.6-0.7 vapor-pressure numbers only on hot, humid days; 0.9 or higher would occur only if it's raining cats and dogs.

Inputing the right barometric pressure is one of the most important factors in obtaining accurate corrected torque and power numbers. Traditionalists still rely on a wall-mounted mercury barometer, but its reading must be corrected for temperature and gravity.

Humidity When the humidity increases, octane requirements ease. The formula is something like... for every one gram of water increase per one kilogram of dry air the octane decreases by .25 to .35. WWII aviation engines used water injection and it worked well for a short time by cooling the cylinder temperature. As temperature goes back the effect goes away.
Many people think that the dyno is the "all knowing, almighty," last word. Nothing could be farther from the truth.